The present invention relates to needle assemblies with anti-backflow features, and more particularly, concerns such a needle assembly with anti-backflow characteristics without the inclusion of an operative valve or like device within.
In the collection of fluids, and especially when such fluids may be blood or other bodily fluids from a patient, it is highly desirable that backflow into the patient be prevented, or at least delayed for a substantially long time period. The reasons for prevention of fluid back into the patient are numerous. For example, when collecting blood into a collection container, various chemicals or other reagents may be present in the container for different tests on the blood sample. As the blood sample flows into this container, it mixes with the chemical therein. Should this mixture backflow into the patient, the chemical would then enter the patient's blood stream with potential harm to the patient. Another instance where backflow into the patient could be problematical involves clotting of the blood during the collection procedure. Should a small amount of the collected blood clot somewhere in the collection needle or container, backflow of such a clotted or coagulated amount of blood into the patient could cause serious difficulties. Accordingly, the inclusion of some type of anti-backflow mechanism into a needle assembly for the collection of fluids from a patient is a desired feature.
In prior attempts at controlling this undesirable backflow of blood or bodily fluid, reliance has been placed particularly on the use of various types of valves. These valves have been proposed in various shapes and forms, notably including shiftable ball valves, cup valves, disk valves with a self-sealing slit therein, "duck bill" valves and the like which open and close under differential fluid pressures. Other types of valves may also have been proposed. These valves are all based on an operative component whereby either fluid pressure, needle puncture, or force of the moving fluid causes the valve to open and close depending upon the respective direction of fluid flow. In addition to the expense of manufacture involved in these small, somewhat intricate valve devices, the difficulty involved in mounting the same into a small needle assembly and attendant problems in handling the same, an operative valve of this nature takes on another risk, namely involving its functionability. When reliance is placed upon an operating valve, there must be significant assurance that the valve will operate according to its intended purpose and design. If the valve fails to operate, then backflow of blood or other bodily fluid into the patient will not be prevented. Therefore, with such an operative element included in the needle assembly, it must be concluded that there is always a risk that the valve will not operate properly with potential harmful consequences. Therefore, a straightforward mechanism for preventing or, at least, delaying backflow of blood or the like fluids into a patient during the blood collecting procedure is still being sought. This mechanism is one which not only will operate effectively, but minimize or completely eliminate the attendant risk involved with operative valves as described above. It is to the solution of this problem which the present invention is directed.